Except they don't say who the author is. If you want to help the author spread their work, saying who it is would help people find their work. Providing a link to the original would be the next step beyond. So it is like keeping the money as a business owner, but saying that it's all thanks to your wonderful employees. Or throwing them a pizza party for the record breaking profits they made that year.

You see this a lot with reposted art. A repost on a Twitter account that does nothing but repost art? 10k likes, no mention of who the original artist is. The original piece on the artist's Twitter account? 127 likes.